What is digital valve control technology?

Valve-controlled hydraulic systems rely on the opening of the control valve to control the speed of the hydraulic components. The hydraulic valve has changed from the early manual valve to the electromagnetic directional valve, and then to the proportional valve and servo valve.

 

The development and popularization of electro-hydraulic proportional control technology has enabled the control technology of engineering systems to enter the ranks of modern control engineering. The hydraulic components that constitute the electro-hydraulic ratio technology have also been further developed on this basis. Traditional hydraulic valves are easily affected by load or oil source pressure fluctuations.

 

In response to this problem, load-sensing technology uses a pressure compensator to keep the valve port pressure difference approximately constant. The system pressure is always compatible with the highest load pressure to minimize energy consumption. The load-sensing system of the multi-way valve cannot realize simultaneous operation of multiple cylinders when the demand flow of the actuator exceeds the maximum flow of the pump. The anti-flow saturation technology realizes that the pressure difference of each pressure compensator changes at the same time to realize the working speed of each load to keep the original set ratio unchanged.

 

The emergence of digital valves, their close integration with sensors and microprocessors greatly increases the freedom of the system, enabling the valve control system to combine multiple control methods more flexibly.

 

The control and feedback signals of the digital valve are all electric signals, so there is no need for additional hydraulic components such as shuttle valves or pressure compensators. The pressure and flow parameters of the system will be fed back to the controller, and the electro-hydraulic flow matching control technology will be applied to control the pump displacement according to the valve signal.

 

The electro-hydraulic flow matching control technology adopts the synchronous parallel control of pump and valve, which can basically eliminate the phenomenon of pump lagging valve in traditional load-sensing system control. The electro-hydraulic flow matching control system is committed to combining the advantages of the traditional mechanical-hydraulic load-sensing system, electro-hydraulic load-sensing system and positive flow control system, giving full play to the flexibility and flexibility of the electro-hydraulic control system, and improving the damping characteristics and energy saving of the system.

 

Compared with the traditional hydraulic valve spool inlet and outlet linkage adjustment, the oil outlet relies on the balance valve or the one-way throttle valve to form back pressure, which brings the disadvantages of poor flexibility and high energy consumption. At present, the high-speed on-off digital valves studied at home and abroad basically use load port independent control technology, so as to realize the separate adjustment of the pressure and flow of the oil inlet and outlet.

 

Aalborg University in Denmark studied the influence of independent control strategies and valve structural parameters on the performance of independent control of the load port.

 

Purdue University in the United States used 5 poppet valve combinations to study robust adaptive control strategies to achieve trajectory tracking control and energy-saving control. Among them, 4 poppet valves realize independent control function of load port, and one middle poppet valve realizes flow regeneration function.

 

The research and application of electro-hydraulic proportional control technology, electro-hydraulic load sensing technology, electro-hydraulic flow matching control technology and load port independent control technology have further improved the control accuracy and energy saving of hydraulic valves. The development of digital hydraulic valves will inevitably be combined with these valve control technologies to improve the accuracy and flexibility of control.